1. Field of the Invention
This invention relates generally to an optical angle of arrival measurement system.
2. Description of the Related Art
High precision and large field of view optical angle of arrival measurement is a critical task in adaptive optics, laser communications, target tracking, optical surveying, and many other applications. Current solutions are limited either by resolution or field of view (FOV) due to inadequate focal plane array (FPA) size and detector noise. Conventionally, a lens converges incoming light from a fixed location point source onto an FPA that has M (row)×N (column) pixels. The focused spot on the FPA is circular (e.g., having a Gaussian intensity distribution) and occupies about Y×Y detector pixels. The position (x, y) of the focused spot on the FPA is determined, from which the optical angle of arrival is calculated as θx∝x/f, θy∝y/f, where f is the focal length of the lens. Using a simple peak searching algorithm, the resolution (δθ) of the angle of arrival measurement will be proportional to d/f, where d is the FPA pixel width, the FOV in horizontal will be proportional to
            tan              -        1              ⁡          (              Nd                  f          ⁢                                                    )        ,and the FOV in vertical will be proportional to
            tan              -        1              ⁡          (              Md        f            )        .Improving resolution requires reducing pixel size (d) and/or increasing focal length (f), both of which reduce the FOV. The state-of-the art solution is to fabricate the FPA with small pixel size and a large number of pixels. However, such an FPA is expensive to fabricate. Furthermore, a large number of pixels will slow down the frame rate of the sensor and increase the processing time required to determine the spot location. In general, the precision of any similar optical direction of arrival sensor is limited by the accuracy of the ability to determine the location of a single focused spot on the FPA with subpixel precision.